1. Field of the Invention
The invention relates to the field of earth boring tools and more particularly to packaging for printed circuit boards in earth boring tools which are subject to high vibration and temperature environments.
2. Description of the Prior Art
Printed circuits used in high temperature and high vibration environments, like in downhole oil tools, must be insulated or protected from high vibration levels and temperatures or else circuit failure is highly probable. Traditionally the circuits are simply potted in their circuit packaging with a rigid molded in place insulator. However, if a circuit element fails or any type of circuit modification is required, the potting must be laboriously chipped away, sandblasted or dissolved without damaging those circuit elements which are sought to be saved. This has resulted in the virtual impracticability of repair or modification on any downhole circuit package.
In an attempt to over come this limitation of prior art packaging techniques, practitioners have packed a circuit package with a resilient foam or filler instead of a molded-in-place dielectric. This results in various ones of the components on the printed circuit board bearing a higher load than other elements. The result is that the more highly loaded circuit components tend to be damaged by high vibration causing premature failure.
What is needed is a method and packaging which will protect a printed circuit from heat and vibration loads, which will allow easy repair or modification, and which will not result in premature failure of any of the circuit elements.